There are three types of restart datasets generated by the model: master, secondary, and history buffer restart files. Each dataset is in binary format and contain grid-point data and other information necessary to continue or branch a model run.
Upon restart, a simple ASCII text file (the "restart pointer file") is read to obtain the full pathname of the most recently written master restart file. Only the name of the master restart file is needed as input for a continuation run. The other files needed for restart (such as secondary restart files, or history files that need to be opened) are also listed in the restart pointer file. The Master restart file itself includes the full archive path to the files that actually need to be opened.
Master restart files are always written during a model run. A secondary restart file is written if absorptivity/emissivity is not be calculated on the first timestep after restart, and therefore must be saved on a restart dataset. For a stand-alone run this occurs if the first history file series write frequency, NHTFRQ(1), is not a multiple of the absorptivity/emissivity calculation frequency, IRADAE (note that for a CCSM flux coupled run, only the flux coupler determines when the restart files are written). It is advisable to avoid this situation if possible, since this dataset is relatively large even for the standard T42 model.
A history buffer restart file is written in order to retain the accumulated values in the history buffers if restart files are to be written on a timestep when one or more history file time samples are not written. A separate restart dataset is written for each history file. Each history buffer restart file contains the portion of the history buffers pertaining to that history file.
All restart files have names of the form $CASE.cam2.r.yyyy-mm-dd-sssss, but with the ".r." changed to the appropriate restart filename. For example, ".r." is for the master restart filename, while , ".ra." corresponds to the absorptivity/emissivity restart filename, and ".rh0." is the first history file series restart filename. In the root name, $CASE refers to the caseid, yyyy corresponds to the year (note more than 4 digits for the year will be used if necessary), mm is the month, dd is the day and sssss is the seconds of the date yyyymmdd. The following is an example of the restart files written during a simulation.